The present invention relates to a circuit board and to a method for making a circuit board and, more particularly, to a multi-layer circuit board and to a method for making a multi-layer electrical circuit board having air-bridges and/or crossover circuits and further having metallized apertures which are selectively formed through the board and which may be selectively connected and/or detached and/or isolated from an electrical ground plane.
Multi-layer circuit boards allow electrical components to selectively and operatively populate opposed surfaces of each board (or other respective interior portions of each of the boards), thereby desirably allowing each of the electrical circuit boards to contain a relatively large amount of electrical components which efficiently and densely populate the respective boards. It is desirable to allow each of the component-containing surfaces or portions of a created and/or formed electrical circuit board to communicate and/or be selectively interconnected, thereby allowing the contained electrical components to cooperatively and selectively form one or more desired electrical circuits. This desired communication and/or interconnection typically requires the use of shared electrical ground planes, the transmittal of power and/or control type signals between each of the component containing surfaces or board portions, and/or the connection and/or interconnection of the various contained electrical components.
This desired interconnection typically requires that one or more holes be drilled through each of the circuit boards, thereby physically creating at least one xe2x80x9cthrough holexe2x80x9d or xe2x80x9cviaxe2x80x9d lying between each of the opposed component containing surfaces and through the various interior circuit board portions. Such drilling is undesirable since it is relatively time consuming, costly, potentially causes damage to significant numbers of the formed electrical circuit boards requiring these circuit boards to be destroyed, and requires costly and inefficient electroless and/or electrolytic plating of the formed holes or xe2x80x9cviasxe2x80x9d.
While some attempts have been made to obviate the need for such plating, such as by the use of a conductive epoxy within each of the drilled holes, these attempts have not produced reliable electrical interconnections and these produced interconnections are not typically adapted to allow the communication of electrical power signals between the board surfaces or to securely and reliably allow the formed aperture to securely receive a component.
Further, it is desirable to form xe2x80x9cair-bridgesxe2x80x9d or xe2x80x9ccrossover type circuitsxe2x80x9d upon one or more selected surfaces and/or within certain component containing portions of the formed circuit board in order to allow multiple levels of circuits and/or electrical interconnections to be formed upon a single board surface or within a certain component containing portion of the circuit board, thereby desirably increasing the amount of electrical circuits which may be created upon and/or within the created circuit board.
These air-bridges or crossover circuits are typically formed by rather complicated, costly, and time consuming processes which require successive layers of material to be accurately and precisely aligned by the use of rather complex and inefficient alignment processes and/or methodologies. This alignment process is both time consuming and costly, thereby limiting and/or reducing the desirability of creating these air-bridges or crossover circuits. Further, the formed bridges and crossover circuits do not typically and efficiently accommodate certain desirable circuit board interconnection processes and/or schemes such as and without limitation, the use of relatively heavy wire bonding (e.g., using aluminum wire having a diameter of about five to about twenty milli-meters) or the direct connection of components to a surface of the board.
There is therefore a need to provide a method for producing a multi-layer electrical circuit board which overcomes some or all of the previously delineated drawbacks, which selectively allows grounded and non-ground xe2x80x9cviasxe2x80x9d and/or xe2x80x9cthrough holesxe2x80x9d to be desirably and selectively formed, and which further allows for the efficient and selective formation of air-bridge members or crossover members which desirably accommodate diverse types of circuit interconnection processes and/or schemes.
It is a first object of the present invention to provide a method for producing a multi-layer electrical circuit board which overcomes some or all of the previously delineated drawbacks of prior multi-layer electrical circuit board forming methodologies and techniques.
It is a second object of the invention to provide a method for producing a multi-layer electrical circuit board which overcomes some or all of the previously delineated drawbacks of prior multi-layer electrical circuit board forming methodologies and techniques, which allows for the selective, efficient, and reliable formation of metalized apertures which cooperatively allow for communication by and between and/or interconnection of these various electronic components, and which allows these apertures to be selectively created and/or formed without drilling, and which allows these apertures to selectively, securely, and reliably receive a component and/or an element.
It is a third object of the invention to provide a method for producing a multi-layer electrical circuit board which overcomes some or all of the previously delineated drawbacks of prior multi-layer electrical circuit board forming methodologies and techniques and which allows for the selective formation of metalized apertures which may be selectively connected or disconnected and/or isolated from a selectively formed electrical ground plane or bus.
It is a fourth object of the invention to provide a method for producing a multi-layer electrical circuit board which overcomes some or all of the previously delineated drawbacks of prior multi-layer electrical circuit board forming methodologies and techniques and which allows for the selective and efficient formation of air bridges and/or crossover members which are adapted to accommodate a wide variety of component interconnection assemblies.
It is a fifth object of the invention to provide a method for producing a multi-layer electrical circuit board which overcomes some or all of the previously delineated drawbacks of prior multi-layer electrical circuit board forming methodologies and techniques and which allows the created circuit board to be functionally tested prior to receiving the electronic components.
It is a sixth object of the invention to provide a method for producing a multi-layer electrical circuit board which overcomes some or all of the previously delineated disadvantages of prior multi-layer electrical circuit boards and which allows the various layers of the produced circuit board to be relatively easily and desirably aligned with other layers and/or with the circuit board before they are respectively attached to these other layers and/or to the circuit board.
According to a first aspect of the present invention, a method for making an electric circuit board is provided. The method includes the steps of providing a member having a central layer of a first material which is operatively positioned between first and second layers of a second material; placing a layer of a third material upon certain portions of the first layer, thereby exposing at least one portion of the first layer; placing a plurality of layers of the second material on top of the layer of the third material, effective to form a multi-layer electrical circuit board having an aperture which extends through the formed electrical circuit board and which terminates upon the exposed at least one portion of the top layer.
According to a second aspect of the present invention a multi-layer circuit board is provided. The method includes the steps of providing a member having a central layer of a first material which is operatively positioned between top and bottom layers of a second material; removing a portion of the first and the second layers, thereby exposing portions of the central layer of the first material; providing a first layer of a dielectric material and placing the provided first layer of the dielectric material onto certain portions of the top layer, thereby overlaying the exposed portions of the central layer and creating first and second exposed portions of the top layer; providing a third layer of the second material and placing the third layer onto the first layer of the dielectric material and over the first and second exposed portions of the top layer; removing those portions of the third layer which overlay the first and the second exposed portions of the top layer; providing a second layer of the dielectric material and placing the second layer of the dielectric material onto the third layer after those portions of the third layer which overlay the first and second exposed portions of the top layer have been removed; providing a fourth layer of the second material and placing the fourth layer upon the second layer of the dielectric material and over the first and second exposed portions of the top layer; and removing those portions of the fourth layer which overlay the first and the second exposed portions of the top layer, thereby creating an electrical circuit board having a first aperture which extends through the third and fourth layers of the second material and through the first and second layers of the dielectric material while terminating within the first layer of the second material, and a second aperture which extends through the third and fourth layers of the second material and through the first and second layers of the dielectric material while terminating within the first layer of the second material.
According to a third aspect of the present invention, a circuit assembly is provided. The circuit assembly is made by the process of providing a core member having a central layer of a first material which is operatively contained between a top and a bottom layer of electrically conductive material; creating an registration slot within the core member; placing dielectric material on certain portions of the top layer, thereby exposing a first and a second portion of the top layer, thereby creating a pre-circuit assembly; and using the created registration slot to selectively add layers of electrically conductive material to the pre-circuit assembly, thereby creating a circuit assembly having a first aperture which is formed through the created circuit assembly and which terminates within the first exposed portion and having a second aperture which is formed through the created circuit assembly and which terminates within the second exposed portion.
These and other objects, aspects, and advantages of the present invention will become apparent upon reading the following detailed description in combination with the accompanying drawings.